BIO-151 (Exam 3) Study Guide

Bone Growth in Thickness

1. Bone forms at surface in ridges on either side of periosteal blood vessels • Osteoblasts secrete ECM, become surrounded osteocytes 2. Ridges around blood vessels form tunnels • Periosteum is now endosteum inside bone 3. Osteoblasts in endosteum secrete ECM, form new rings of concentric lamellae

Ossification

1. Initial formation of bones in embryo and fetus 2. Growth of bones during infancy, childhood and adolescence 3. Remodeling of bone 4. Repair of fractures

Muscular Tissue Function

1. Movement: through interaction of skeletal muscles, bones, & joints 2. Posture: stabilize body positions 3. Storage and movement

Bone Remodeling

Bone continuously renews itself throughout life • Includes about 5% of the total bone mass at a time • Bone mass can be increased in response to heavy loads or strain • Allows for extraction of bone minerals to maintain calcium levels in blood • New bone is more fracture resistant than old bone

Enlargement of the Medullary Cavity

Bone tissue lining medullary cavity is destroyed by osteoclasts in the endosteum

Cardiac Muscle

Branched, striated fibers Usually only one nucleus in center of cell

hydroxyapatite crystals

Calcium phosphate + calculate hydroxide

Growth of cartilage model

Chondroblasts----->chondrocytes • Chondrocytes divide and secrete cartilage ECM ▪Interstitial growth (growth in length) • Cartilage in middle begins to calcify• Chondrocytes within calcified ECM begin dying

Periosteum

Connective tissue sheath & associated blood supply. Protection, repair, nourishment, attachment for ligaments & tendons

Structure of Skeletal Muscle Tissue

Connective tissue surrounding muscle fibers In hypodermis, areolar connective and adipose tissue separate skin from muscle Blood vessels Nerves

Histology of Bone

Connective tissue: few cells, much extracellular matrix (ECM). ECM: 15% water, 30% collagen, 55% mineral salts. Also calcium carbonate, magnesium, fluoride, potassium, sodium

Myofibrils

Contractile organelles is skeletal muscle fibers appear as thread-like structures within sarcoplasm (diameter about 2 μm) Extend the entire length of a muscle fiber Striation in myofibrils is source of muscle fiber striation

A band

Darker middle part of sarcomere ▪ Extends entire length of thick filaments

Bone remodeling phase

Dead portions of fracture resorbed by osteoclasts Compact bone replaces spongy bone where needed Osteoclasts remodel bone to original shape

Terminal cisterns

Dilated end sacs found on both sides of a T tubule

Nerve and Blood Supply

Each skeletal muscle penetrated by a nerve, an artery, & 1 - 2 veins ▪ Nerves are somatic motor neurons ▪ Thin axon extends from brain or spinal cord to group of muscle fibers Each muscle fiber is close to 1+ blood capillaries ▪ Active muscle fibers require oxygen, glucose, fatty acids ▪ Blood removes heat and metabolic waste products

Myofilaments

Even smaller filaments within myofibrils Muscle contraction occurs as filaments slide past each other Do not extend length of myofibril▪ Smaller compartments of myofilaments: sarcomeres ▪ Z discs: dense protein separating sarcomeres

Sarcoplasmic reticulum

Fluid-filled membranous sacs surrounding each myofibril Stores Ca2+ in a resting muscle fiber Release of Ca2+ triggers muscle contraction

Factors Affecting Bone Growth and Remodeling

Hormones • Include Insulin-like growth factor (IGF), Thyroid hormones (T3, T4), insulin • Promote cell division, stimulate osteoblasts, enhances bone protein synthesis • Increase of sex hormones (estrogen, androgens) at puberty trigger growth and skeletal changes

Formation of articular cartilage and epiphyseal growth plate

Hyaline cartilage covering epiphyses becomes articular cartilage Epiphyseal (growth) plate: Hyaline cartilage remaining between diaphysis and epiphysis until maturity

Skeletal Muscle

Long, cylindrical fibers with striation (stripes) Multinucleated with nuclei at periphery of cell Voluntary movement controlled by neurons of somatic nervous system Some unconscious control (diaphragm in breathing, posture) Heat production Protection

Myosin

Main component of thick filaments Motor protein in all three types of muscle tissue Converts ATP chemical energy into mechanical energy

Actin

Main component of thin filaments. Actin molecules twist together to form helix-shaped filament Myosin binding sites to bind myosin heads

Exercise and Bone Tissue

Main strain on bone is pull of skeletal muscles and gravity Mechanical strain causes increase deposition of minerals and collagen fibers Athletes have thicker and stronger bones

Smooth muscle

Non-striated spindle-shaped cells with single central nucleus Gap junctions common Motion (usually involuntary), some autorhythmicity to cells of digestive tract

Bone deposition

Osteoblasts add minerals & collagen fibers

Bone resorption

Osteoclasts remove bone minerals & collagen fibers

Compact bone

Osteon: repeating unit within bone • Osteonic (haversian, central) canal: runs through center of osteon ▪ contains blood vessels, lymphatic vessels, nerves • Concentric lamellae: concentric rings in the osteon • Bone lacunae: ("little lakes"): contain osteocytes • Interstitial lamellae: spaces between the osteons

Aging and Bone Tissue

Over time, resorption by osteoclasts outpaces deposition by osteoblasts • Loss of bone mass from demineralization Especially significant to aging in women • Brittleness from decreased protein synthesis with age

Regulation of Blood Calcium Levels

Parathyroid hormone (PTH): increases blood Ca2+ level • Negative feedback system with parathyroid cells acting as receptors • Low blood Ca2+ triggers PTH secretion▪Increases the number and activity of osteoclasts▪Increases Ca2+ reabsorption in the kidney ▪Stimulates formation of calcitriol (active form of Vitamin D), promoting Ca2+ absorption from gastrointestinal tract

Z Disc

Passes through the center of the I band

Sarcolemma

Plasma membrane of muscle fibers Nuclei are located next to sarcolemma

Myosin tail

Points toward the M line in center of sarcomere

Development of medullary cavity

Primary ossification center grows toward the ends Osteoclasts break down some trabeculae, creating medullary cavity Wall of cavity eventually replaced by compact bone

Sphincters

Rings of smooth muscles at exit of hollow organs Cardiac muscle contractions Smooth muscles contract & relax in walls of blood vessels, gastrointestinal tract, gall bladder, reproductive system, & urinary system

Vertebral compression fracture

vertebral body compressed into wedge shape

Zone of overlap

where thick and thin filaments overlap

Periosteal arteries/veins

with nerves enter diaphysis through perforating canals

Bone's Role in Calcium Homeostasis

• 99% of body calcium is stored in bone• Blood level calcium ions (Ca2+) are very closely regulated • Nerve & muscle cells depend on stable Ca2+ level in extracellular fluid • Blood clotting and many enzyme activities require Ca2+ • Osteoblasts and osteoclasts help "buffer" the blood Ca2+ level by bone remodeling

Reparative phase: fibrous cartilage callus formation

• Blood vessels grow into fracture hematoma • Fibroblasts from periosteum enter the fracture s produce collagen fibers • Cells from periosteum develop into chondroblasts and produce fibrous cartilage • Formation of fibrous cartilage (collagen fibers & cartilage)

Osteoblasts

• Bone deposition: synthesize & secrete components of ECM including collagen • Initiate calcification • Differentiate into osteocytes

Intramembranous ossification

• Bone develops directly within mesenchyme mesenchyme = embryonic connective tissue ▪ flat bones of skull, facial bones, mandible, medial part of clavicle

Formation of trabeculae

• Connective tissue differentiates into red bone marrow

Osteoclasts

• Derived from the fusion of monocytes • Ruffled border on bone-surface side • Bone resorption: Releases lysosomal enzymes and acids onto bone • Concentrated in endosteum

Microscopic Anatomy of Skeletal Muscle

• Diameter: 10 to 100 μm • Length: average 10 cm (4 inches) • Multinucleated due to fusion of myoblasts during development • Mature muscle fibers (myocytes) do not undergo cell division Number of muscle fibers is set before birth

Epimysium (outer layer)

• Encircles entire muscle • Dense irregular connective tissue

Reactive phase

• Formation of fracture hematoma • Swelling and inflammation • Blood supply is cut off, nearby bone cells die • Phagocytes and osteoclasts remove the dead bone tissue

Endochondral ossification

• Hyaline cartilage develops from mesenchyme, then replaced by bone

Development of primary ossification center

• Inward from surface • Artery penetrates the perichondrium and cartilage model ▪Stimulates osteoprogenitor cells in perichondrium---->osteoblasts ▪ Perichondrium----->periosteum

Spongy bone

• Located in epiphyses of long bones & the interior of short, flat, sesamoid, and irregular bones • Always found within outer layer of compact bone

Osteocytes

• Mature bone cells • Main cells of bone tissue • Carry out bone metabolism

Development of periosteum

• Mesenchyme at edge of bone develops into periosteum • Thin layer of compact bone replaces spongy bone at surface

Osteoprogenitor cells

• Only bone cell that divides • Differentiate into osteoblasts • Found in inner osteogenic layer of periosteum, in endosteum, & in canals within bone that have blood vessels

Reparative phase: bony callus formation

• Osteoprogenitor cells develop into osteoblasts. • Osteoblasts produce trabeculae • Fibrous cartilage callus is converted into spongy bone bony callus

Endomysium (inner layer)

• Separates individual muscle fibers • Mostly reticular fibers

articular cartilage

Thin layer of hyaline cartilage covering the articulation part of epiphysis. Lacks perichondrium and blood vessels. Reduces friction and absorbs shock

Contractility

ability to contract when stimulated by nerve impulse

Electrical Excitability

ability to produce muscle action potentials (impulses) in response to specific stimuli Chemical stimuli (neurotransmitters, hormones, pH) Autorhythmic response to electrical signals

Elasticity

ability to return to original shape after contraction or extension

Extensibility

ability to stretch within limits without being damaged

Thin filaments

actin protein

Zone of resting cartilage

anchors epiphyseal plate to epiphysis

Muscle fibers

are also called myocyte cells

H Band

area within A band with only thick filaments

Intercalated discs

attach muscle cells together contain gap junctions and desmosomes

Metaphyses

between diaphysis and epiphyses

Myosin head

binds ATP and actin ATP binding site hydrolyzes ATP to generate energy

Myoglobin

binds O2 that diffuses into muscle fiber -found only in muscle -releases O2 when needed

Epiphyseal line

bone has replaced cartilage in epiphyseal plate, bone ceases growth

Comminuted fracture

bone is splintered, crushed, or broken in pieces at the site of impact

Open (Compound) fracture

broken ends of the bone protrude through skin

Vitamin D

calcium absorption in the intestines

Inner osteogenic layer

cell layer enables bone growth

Zone of proliferating cartilage

chondrocytes divide and secrete ECM

Vitamin C

collagen synthesis

interosteonic canals

connect blood vessels/ nerves in medullary cavity, periosteum, & osteonic canals

Calcification

crystallization of mineral salts hardens bone. Initiated by osteoblasts Osteoblasts---->osteocytes Osteoblast deposits calcium into ECM

Sarcoplasm

cytoplasm of muscle fibers -lots of glycogen

Calcitonin

decreases blood Ca2+ level • Produced in thyroid gland • High blood Ca2+ levels trigger CT secretion▪Inhibits activity of osteoclasts▪Speeds uptake and deposition into bone

Outer fibrous layer

dense irregular connective tissue

Fascia

dense sheet of irregular connective tissue Lines body wall and limbs Supports and surrounds muscles and organs Holds muscles with similar functions together Carries nerves, blood vessels, and lymphatic vessels

Closed (Simple) fracture

does not break the skin

Nutrient artery/vein

enter diaphysis of long bones through nutrient foramen ▪ Supply inner compact bone, spongy bone, and bone marrow

Bone Trabeculae

flat plates with network of thin, bony columns, lined with endosteum • No osteons • Have lamellae, bone lacunae, osteocytes, bone canaliculi • Spaces filled with red or yellow marrow, blood vessels

Pott

fracture of distal end of fibula

Colles

fracture of radius where the distal fragment is displaced posteriorly

Thermogenesis

generation of heat

Periosteal capillaries

grow into the calcified cartilage ▪Induces growth of primary ossification center in center of bone ▪Trabeculae form in the calcified cartilage

Appositional growth

growth at outer surface of tissue Cells in inner cellular layer of the perichondrium differentiate into chondroblasts, chondroblasts surrounded with extracellular matrix & become chondrocytes Matrix accumulates beneath the perichondrium on outer surface of cartilage Continues through adolescence

Interstitial growth

growth within the tissue Division of existing chondrocytes & deposition of increasing amounts of extracellular matrix Childhood and adolescence

Troponin

holds tropomyosin in place

Medullary Cavity

hollow space within diaphysis. Contains fatty yellow bone marrow and blood vessels

Titan

huge, elastic protein stabilizes thick filament from Z disc to M line

epiphyseal growth plate

hyaline cartilage allows diaphysis to grow in length

Tropomyosin

in relaxed muscle, blocks myosin from binding to actin

autorhythmicity

involuntary alternating contraction and relaxation Blood pumping to body adjusted by hormones & autonomic (involuntary) nervous system

Minerals

large amounts needed, especially calcium and phosphorus

Zone of hypertrophic cartilage

large maturing chondrocytes

Dystrophin

links thin filaments to integral membrane proteins of sarcolemma

Glycogen

macromolecule made of glucose -glucose is used in ATP synthesis

Thick filaments

myosin protein

Impacted fracture

one end of bone firmly driven into interior of other end

Greenstick fracture

one side of bone is fractured, other side bends

Mitochondria

produce ATP to provide energy for muscle fibers

Hemopoiesis

produce blood cells and platelets in red bone marrow

Epiphyses

proximal and distal ends of the bone

Zone of calcified cartilage

replacement by bone in progress

Vitamin A

stimulates osteoblasts

Mineral Homeostasis

store and release minerals

Triglyceride storage

stored in adipocytes in yellow bone marrow

Metaphyseal artery/vein

supplies the metaphyses

epiphyseal artery/vein

supply the epiphyses

Vitamins K, B12

synthesis of bone proteins

Perforating fibers

thick bundles of collagen extend from periosteum into bone extracellular matrix. attaches collagen to bone

Bone canaliculi

thin channels connect bone lacunae ▪ allow nutrients to diffuse to osteocytes ▪ osteocytes extend processes through canaliculi & communicate with each other via gap junctions

I Band

thin filaments only

Endosteum

thin membrane lining medullary cavity. Contains bone‐forming osteoprogenitor cells and connective tissue

T tubules

Tunnels of sarcolemma toward center of muscle fibers -Filled with interstitial fluid -Allows fast spread of action potential across sarcolemma

Development of secondary ossification centers

Usually around time of birth Arteries entering the epiphyses stimulate formation Spongy bone in center of epiphyses ▪ No medullary cavity in epiphyses Outward from center to surface

Diaphysis

Shaft (body)

Function of Bones

Skeletal framework: support soft tissues, attachment sites for tendons. Protection of internal organs. Work with muscles to produce movement

M Line

Supporting proteins hold thick filaments together at the center of the H band

Perimysium (middle layer)

Surrounds muscle fascicles (bundles of 10 - 100+ muscle fibers) Dense irregular connective tissue